Explosion-proof lighting equipment



Aug. 24', 1948. D. A. TUCK 2,447,922

EXPLOSION-PROQF LIGHTING EQUIPMENT Filed July 12, 1944 lNVE NTOR DAV/3H.TUCK ATTORNEY Patented Aug. 24, 1948 EXPLOSION-PROOF LIGHTING EQUIPMENTDavis H. Tuck, Bedding Ridge, Conn., assignor to Holophane Company,Inc., New York, N. Y., a corporation of Delaware Application July 12,1944, Serial No. 544,568

4 Claims. 1

The present invention relates to explosionproof lighting equipment.

Lighting equipment designed for ordinary indoor use is not suitable foruse in hazardous locations. There are two classes of locations wherespecial precautions must be taken in the type of lighting equipment. Oneclass of such locations is that in which flammable volatile liquids,highly flammable gases, mixtures or other highly flammable substancesare manufactured, used, handled, or stored in other than their originalcontainers. This class may include such locations as some parts ofdry-cleaning and dry-dyeing plants, pyroxylin plastic manufacturingplants, spray painting establishments, flammable-gas plants,varnish-manufacturing plants, distilleries, rectifying and blendingplants producing whiskey and other alcoholic beverage liquors, plantsproducing industrial alcohol, and establishments or industries involvingsimilar h'azardous processes or conditions. Thesecond class of locationsis that in which (1) combustible dust is thrown, or is likely to bethrown, into suspension in the air in suflicient quantities to produceexplosive mixtures or (2) those where it is impracticable to preventsuch combustible dust from collecting in such quantities on or inmotors, lamps, or other electrical devices that they are likely tobecome overheated because normal radiation is prevented. This class mayinclude such locations as some parts of flour mills, feed mills, grainelevators, starch plants, sugar, cocoa and coal pulverizing plants, andestablishments or industries involving similar hazardous processes orconditions.

Owing to the special construction necessary for such vapor-tight anddust-tight equipment the cost of the equipment is much greater than thecost of equipment having equivalent light sources, and in many cases theequipment necessary to take care of the hazardous conditions makes thelighting equipment far less emcient than it would be if it could bedesigned along more efilcient lines. The loss in efiiciency thereforemay make it necessary to employ more of the more expensive equipment toobtain the lighting results required.

The present invention contemplates lighting equipment which isconstructed along the conventional lines used in making dust tightequipment and provided with suitable means whereby a small amount ofcarbon tetrachloride may be retained as a liquid in the totally enclosedunits. According to the present invention this carbon tetrachlorideproduces a mixture of vapors in air which is effective in preventing allpossibility of explosion even when the fixture is charged with explosivegases such as acetylene, illuminating gas, gasoline, ether and the like.

To facilitate maintenance of the lighting units having the individualcharges of carbon tetrachloride, these units have some form of liquidcontainer which is visible externally of the unit, for example, a sumpor well in the glass globe, a gauge glass, or a transparent containerback of a transparent window in the side wall of the unit. This affordsa tell-tale so that one can ascertain by simple inspection of theinstalled fixture that the fixture is actually safe. Explosion-prooffixtures heretofore available looked the same on inspection, whetherthey were safe or not.

In carrying out the present invention based on the use of carbontetrachloride for preventing explosions it is not necessary to designthe equipment strong enough to withstand the pressures developed frominternal explosions. The carbon tetrachloride prevents any explosion sothat there is no need of designing to protect against an internalexplosion. While the carbon tetrachloride will form vapors and some ofthe vapors may escape so that in time the lighting equipment needs to berechecked to see that it is still safe such routine inspection may becarried on at the same time as other inspection of the equipment. Insome cases the escape of carbon tetrachloride vapors into thesurrounding air would be objectionable on account of the odor so thatsuch equipment would not be suitable, but the presence of such a vaporwould be a ready indication of leakage from the lighting equipment, andthis would call for checking the condition of the fixture and possiblyreplacing the carbon tetrachloride lost. In most locations, however,where explosion proof equipment is employed there are variousdisagreeable odors so that the addition of minute quantities of carbontetrachloride to the air would be inconsequential.

The accompanying drawings show, for purposes of illustrating the presentinvention, three embodiments in which the invention may take form, itbeing understood that the drawings are illustrative of the inventionrather than limiting the same.

In these drawings:

Figure 1 is a vertical sectional view with parts in elevation through apendent incandescent lamp type of lighting equipment;

Figure 2 is a perspective view of a fluorescent lighting unit; and

Figure 3 is an enlarged vertical sectional View through the wall of theequipment of Figure 2.

In the arrangement shown in Figure 1 the fitter I is in the form of aone piece casting with explosion proof junction box and connection pieceat the top as indicated at I I and a seal-off fitter as indicated at l2.The fitter supports a lamp socket i3 and :lamp M in the usual manner andis threade'd as indicated at I5 to receive the .upper threaded end of anenclosing globe Hi. This globe may be of any suitable form and shape. Itis here shown as having a glass reflector i1 and a prismatic glassrefractor I8 welded together at I9, The enclosing globe has awell 20 atthe bottom sufficient to hold a. small quantity, -=for example, 2-3 oz.of carbon tetrachloride.

In the arrangement shown in Figure 2 and 3.the fluorescent lightingluminaire 30 is of "any suitable dust tight totally enclosingconstruction. While the receptacle for the carbon tetrachloride might beplaced in the fixture in various .manners, .a convenient arrangement forsupporting .the carbontetrachloridelis indicated in the drawings. Herethe side wall 31' of the luminaire body is provided with anopeningindicated :at 32, Figure3, and-opposite this opening is carriedacontamer- 33 for carbon tetrachloride. This container may convenientlyhave a vertical wall Manda pocket forming well 35. This containerislmadeof transparentiglass and is secured to a mounting member 36 whichmay conveniently be inthe formof a casting of a proper contour tofit'the wall of thefiuorescentfixture. Itisprovided with a .plug 31 tofacilitate refilling the container.

Lighting equipment such as indicated inFigures 1,--2'and.3 willbe-rendered completely explosion-proof by reasoniof the "presence of thecarbontetrachloride vapors in it. Experiments have shown that suchfixtures cannotbe blown up by generatinga spark idischarge inside thefixture when the fixture -is filled with air and gasoline, ether, .orother "flammable gases.

Since it is obvious that the invention :may be embodied in other=formsand constructionswithin the scope of the claims, .I wish'it to beunderstood thatthe particular forms "shown are but a few of these forms,and various modifications .and changes being possible, I do nototherwise :limit myself in any .way with respect thereto.

ing the lamp, alight transmitting enclosing globe about the lampand'secured to the fitter with a substantially gas tight jointtherebetween, a well -in :the bottom of the globe and liquid carbontetrachloride in the Well and observable through the well from beneaththe fixture.

3. A fluorescent lighting fixture for use in hazardous locations,comprising an open mouthed, dust and gas tight metal housing, a lighttransmitting closure across themouth of the reflector, a transparentcontainer carried .byahous ing wall, the wall'having a Window forobserving the .container, and carbon tetrachloride'in thecontainer. 4. Alighting fixture for use in hazardouslocations, comprising an electriclightv source having .an enclosing envelope, a substantially gas tighthousing for the light source, a light transmitting liquid receptacleopening into the .housing and carbon tetrachloride in thereceptacle,whereby carbon tetrachloride vapors may vmix with the air .inthehousing, a portion of the housing being light transmitting so thatthecontentsiof the-receptacle are visible .therethrough from beneaththefixture.

DAVIS H. TUCK.

REFEREN'CES CITED The :following references .are .of '.record in thefile :of this patent:

UNITED STATES .P A'IENTS Number Name Date 459,872 'Tommasi Sept. 22,1891 583,959 'Waegel June 8, 1897 1,607,562 :Potter :Nov.'16, I9261;973,132 Wheat .Sept. 111,1934 2,151,801 Rolph Mar. 28,l1939 2,317,426Wilson .Apr." 27, 1943

